This invention relates to a novel offroad agricultural vehicle. More specifically, this invention relates to an offroad agricultural vehicle with articulated steering to be used as a crop pesticide sprayer, fertilizer applicator, and the like.
Across the United States and throughout the world, offroad agricultural vehicles are used to spray pesticide, apply fertilizer, and perform countless other functions. These vehicles must be extremely versatile and well suited for use within often harsh agricultural environments and uneven terrain.
In the agricultural field, it is sometimes desirable to utilize a vehicle wherein the front and rear wheels of the vehicle traverse coincident paths. In order to simplify vehicle design and minimize cost, the wheels of such a vehicle are restrained from pivoting about the wheel axle. When a change of direction is desired, front and rear frames of the vehicle pivot relative to each other to effectively steer the vehicle. While the basic concept of a vehicle with articulation steering has been known, many unresolved disadvantages have been occasioned in the past.
One of the first articulation steering machines was a tractor having two frames which articulate about a universal joint. A rack and pinion gear of crude design were provided as part of a steering assembly. The pinion gear moved along the rack and pivoted to translate an operator's steering signal to a corresponding pivoting of the two frames, thereby effecting steering.
One disadvantage to this configuration was the limitation on load capacity due to the single universal joint. Because the force of the load is delivered to the single universal joint, the friction force tends to bind the shaft housings of the two frames together and thereby decrease the ease of rotation of the two frames relative to one another. Moreover, such previously known vehicle frames were not sufficiently strong to support the weight of tanks which are presently used to carry insecticide, fertilizer, or the like. A further disadvantage to the above described vehicle was that steering effected by movement of the pinion along the rack adds another pivot point to the vehicle. The vehicle steering is therefore rather complex which then complicates operation of the vehicle. Still further, the steering ability of the vehicle is adversely affected when traversing uneven ground because engagement of the rack and pinion device may be disrupted as the two frames oscillate over an undulating terrain.
The difficulties suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness and operator satisfaction with prior articulation steering vehicles. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that offroad agricultural vehicles appearing in the past will admit to worthwhile improvement.